Machine Learning

Create a Formula from a String

In the most basic case, use as.formula():

This returns a string:

"y ~ x1 + x2"
> [1] "y ~ x1 + x2"

This returns a formula:

as.formula("y ~ x1 + x2")
#> y ~ x1 + x2
#> <environment: 0x3361710>

Here is an example of how it might be used: These are the variable names:

measurevar <- "y"
groupvars  <- c("x1","x2","x3")

This creates the appropriate string:

paste(measurevar, paste(groupvars, collapse=" + "), sep=" ~ ")
> [1] "y ~ x1 + x2 + x3"

This returns the formula:

as.formula(paste(measurevar, paste(groupvars, collapse=" + "), sep=" ~ "))
> y ~ x1 + x2 + x3
> <environment: 0x3361710>